Principles of Animal Nutrition: Procedure

Procedure

Weighing procedure view video..
Two gram of feed is accurately weighed. view video...
Accurately measure 200 ml of 1.25% H₂SO₄in a 600 ml spoutless beaker. view video
Place beaker over an electric heater and keep a suitable condensing flask (round bottom) over the beaker. view video
See that the condensing flask fixes well over the beaker leaving no space. The condensing flask is filled with cold water.
Now switch on the heater. The purpose of keeping a condensing flask filled with cold water is for condensing back the evaporating acid to the beaker. This maintains the volume of the acid without any reduction. view video
The beaker is heated to bring the acid (H₂SO₄ 1.25%) to boiling stage. Then 2g of substance is transferred to the boiling acid. The acid boils and the feed is digested in acid. view video
This boiling and digestion is continued for 30 minutes. (Note the time with the help of stopwatch)
After the end of 30 minutes stop the boiling and remove the condenser. Set up a funnel in a large conical flask. view video
Fix a linen cloth over the funnel. Transfer the contents from the beaker to the filtering funnel. After the transfer of all the acid and acid digested residues to the linen cloth, wash the beaker with distilled water and transfer the contents to the filtering funnel. view video
Continue the washing till the residue is made acid-free. view video

Test:

This is tested simply by catching one or two drops of filtrate over blue litmus. If the blue litmus remains blue, that means the residue is washed free of acid.
After complete washing take the filter cloth along with the residue, squeeze well to remove the water from the residue. view video
Place the cloth over porcelain slab. Scrap gently the adhering residue from the filter cloth and keep the residue in the centre of the filter cloth. view video
The acid digested residue is then subjected to alkali digestion. For this 1.25% sodium hydroxide solution is used.
As in the acid digestion, pour 200 ml of sodium hydroxide (1.25%) into a spoutless beaker (600 ml capacity). view video
Place over the heater and fix a condensing flask over this. Bring the alkali solution to boiling stage by heating. view video
When it starts boiling, remove the condensing flask and transfer the acid digested residue to the boiling alkali. Replace the condensing flask and continue the heating. view video
The residue should be digested in the boiling NaOH for a period of 30 minutes.
After 30 minutes, remove the condenser, transfer the contents of the beaker to a filtering funnel. The residue is washed repeatedly with distilled water till it is alkali free. view video

Test:

This is tested by catching one or two drops of the filtrate over red litmus. If it remains red it indicates that the residue is free from alkali. view video
When the residue is free from alkali squeeze the cloth well to dry the residue. view video
Transfer the residue, without any loss, to a clean silica crucible. view video
Note: The cold water in the condensing flask should never be hot at any time. If the water is hot replace it with cold water. Before removing the condensing flask care should be taken to avoid the loss of any residue sticking to the bottom of the flask, if any.
The crucible is placed in preheated hot air oven (110 º C) over night. This is to drive off the moisture completely. view video
After complete drying, the crucible is cooled in desiccator. view video
Weighing procedure view video
It is weighed along with the residue. view video
Heat the crucible with electrical Bunsen in order to ash the residue. Continue the heating till you obtain a whitish ash. view video
Cool the crucible to room temperature and find out the weight. view video
Weighing procedure view video
Find out the weight view video

Calculation

The difference in weight of the crucible before and after ashing is reported as the crude fibre content of the feed taken.
Weight of the sample = X g
Weight of crucible with dry residue = Y g
Weight of crucible with ash = Z g
Weight of the crude fibre = Y-Z g

Last modified: Wednesday, 28 March 2012, 6:35 AM